Master cylinder



April 17, 1945.. J. G. lHAWLEY MASTER CYLINDER 3 Sheets-Sheet l Filed Aug. 19, 1940 ma., w. Nb

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J. G. HAWLEY MASTER GYLINDER Filed Aug. v19, 1940 l sheets-sheet 2 Jsse @Hawlw April 17, 1945.

J'. G. HAWLEY MASTER CYLINDER Filed Aug. 19, 1940 3 Sheets-Sheet 3 jme/wm JsseaH'awzey,

April 17, 1945.;

.m @www small piston assembly is caused to break or collapse as set forth below.

Two pairs of toggle links 12, 13 and 14, 15 are pivoted, at one end, at 16 and 11, respectively, on the lugs 6| and on pivot pins 18. The latter are mounted in ears 88 carried by the operating head 10. The opposite end of each toggle link is pivotally secured to a pivot pin 8|. As shown in Fig. 2, pivot pin 8| is mounted off-center slightly (for example 55), in the direction of an operating angular extension disclosed below, with respeci; to the line connecting the pivots 16, 11. Toggle links 12, 13 terminate, near the.intermediate pivot pins 8|, in lateral flanges 82, 83, respectively, and, near their pivots on lugs 6|, in right angular extensions 84. The latter are adapted, when the piston rod 65 is pushed forward, to contact a projection 85 on flange 35 and swing links 12, 13 outwardly on lugs 6|, as shown in Fig. 3. This causes the intermediate pivot pins 8| t0 also swing outwardly and carry the inner ends of links 14, 15 with them, thus swinging the outer ends of links 14, 15 on their pivot pins 18, against the pressure of coil springs 86, also carried by the pins 18. As shown, the lateral flanges 82, 83, on toggle links 12, 13, limit the downward travel of the intermediate pivot pins 8| under the influence of coil springs 86. Suitable washers 81 and cotter pins 88 are provided to retain the links 12, 13, 14, 15 on their respective pivots.

A coil spring 89 is telescoped around the small piston 65 and bears against the reduced end 51 of piston block 50 and the operating head 10, tending to keep these parts in the position shown in Figs. l, 2, and 6.

Nut 58 also carries a guide rod 90, which has a right angular extension 9| that is threaded at 92 and is adapted to pass through an orifice 93 in peripheral flange 35, to prevent the turning of large piston 23 with respect to fluid cylinder 2 A nut 94, threaded on the right angular extension 9| of guide rod 90, is adapted to limit the outward travel of piston 23.

Small piston 65, after passing through large piston 23, passes through a resilient cup washer 95, which acts as a seal for the operating fiuid in chamber 54, and thence through a resilient washer 96 that is protected on opposite sides by metal washers 91, 98. This washer assembly is clamped between the inner end 4| of fluid chamber unit 22 and the end of uid cylinder 2| bythe adjustment of chamber unit 22. A washer |00, preferably of copper, is preferably inserted between these members. A coil spring ||J|, telescoped around piston 65, bears against washer 91 and l keeps the cup washer 95 in contact with the inner end of piston block 50, to restrict the passage of fluid thereby.

Inlet port 3| preferably communicates `with a fluid reservoir (not shown). Similarly, outlet port 34 communicates with the mechanism (not shown) which it is desired to actuate bythe operation of the master cylinder.

With the master cylinder in the position shown in Fig. 6, large piston 23 is withdrawn to the right sufficiently to permit coil spring |l to force resilient cup washer 95 to uncover orifice 33 and allow fluid from the reservoir (not shown) to enter cylinder 2| and pass through washer assembly 96,

91, 98 into fluid chamber 22. When operatingr head is depressed, the parts are changed to the position shown in Fig. 2, piston 23 being moved to the left sufficiently to close orifice 33 in inlet port 3| and prevent ingress of further fluid from the' fluid reservoir. Small piston 65 yhas alsoentered pedal travel.

13 are also ready to contact projection 85. Upon any further movement of operating head 10, coil spring 89 is compressed and the contact of eXtensions 84 with projection 85 swings toggle links 12, 13 outwardly on pivots 16 and starts the toggle action, as shown in Fig. 3. This also causes piston rod 65 to enter fluid chamber 22 and displace fluid therefrom through orifice 45 into the circumferential recess 46, and thence through outlet port 34 to the mechanism to be actuated thereby.

Upon releasing operating head 10, spring 89 forces it outwardly to the position shown in Fig. 6, toggles 12, 13, 14, 15 are straightened with the aid of springs 86, resilient cup Washer is forced against piston block 50 by spring IUI, orifice 33 is uncovered, and the resulting reduced pressure ,created in cylinder 2| draws in fluid from the fluid reservoir (not shown).

The master cylinder may be made of any suitable materials, but if made for aircraft use, it would be of light construction, such as aluminum alloys or magnesium, and, in this event, a thin steel cylinder would be pressed inside the main cylinder to reinforce it.

From the above description, it will be apparent that my improved master cylinder is not only eilicient in operation, but that it is simple in construction and may be manufactured inexpensively because it eliminates unnecessary linkage and valves. It is adjustable, by means of nut 94, to vary the volume of fluid supplied, to take up all slack in the brake or other mechanism to be actuated thereby. Furthermore, the fluid is automatically transferred from the large low pressure cylinder to the smaller diameter high pressure chamber, and the resulting apparatus comprises a direct acting master cylinder which will supply the required volume of fluid with a minimum of The washer assembly 96, 91, 98, in conjunction with the small lpiston 65, prevents the escape of fluid from the high pressure chamber into the low pressure ,cylinder while the fluid is being displaced from the former to the mechanism to be actuated by vthe maste-r cylinder.

A particular use for which my new master cylinder is adapted is for applying automobile brakes, but it is also adapted for applying airplane brakes and, in general, may be used, wherever a power unit is needed for supplying fluid pressure.

As many apparently widely different embodiyments of this invention may be made without departing from the spirit thereof, it is to be understood that I do not limit myself to the foregoing embodiments or description except as indicated in the following claims.

I claim:

l. In a master cylinder, the combination of a fluid cylinder, a fluid chamber in communication with the fluid cylinder, a large piston, and a small piston assembly, the latter including a small piston passing through the large piston and being provided with toggle links for normally causing the small piston assembly to move with the large piston, an angular extension Ion one oi the toggle links and :a rib carried by the fluid ycylinder to collapse the toggle links .at ea predetermined point in the travel of the small piston and permit the latter to be advanced through lthe large piston and into the fluid chamber to cut off communication between the fluid eynnder and the fluid 'A chamberv and. displace fluid 'from the latter.

2. In a `masterl cylinder, the combination of` a fluid cylinder, a uid chamber in communicationwith the ui'd cylinder, a large piston, and a small n piston assembly, the latter including a small piston passing through the large piston and, being provided with toggle links for normally causing the small piston assembly to move with the large piston, an angular extension on one of the toggle links and a rib carried by the uid cylinder to collapse the toggle links at a predetermined point in the travel of the small piston and permit the latter to be advanced through the large piston and into the fluid chamber to cutoff communication between the fluid cylinder and the fluid chamber and displace fluid from the latter, and an additional means for limiting the outward movement f of the small piston.

3. In a master cylinder, the combination of a withthe fluid cylinder, a large piston, and a small piston assembly, the latter including a small piston passing through the large piston and toggle links and means for normally maintaining them in a position substantially parallel to that of the small piston, and a stop interposed in the path of the toggle links for displacing them from their normal position at a'predetermined point in the fluid cylinder, a fluid chamber in communication travel ofthe small piston to permit the latter to be advanced through the large piston and into the iiuid chamber to cut off communication be.v tween the fluid cylinder and the fluid chamber and displace fluid from the latter.

4. The master cylinder of claim 3, in which the fluid cylinder is provided With an inlet port and the large piston comprises a piston block provided with a circumferentia1 recess, a resilient packing ring at one side thereof, and a terminal flange at the opposite side thereof recessed around its periphery, a resilient Washer; a spring for maintaining the Washer in contact with the end of the piston block' and adapted, upon the outward movement of the small piston, to uncover the inlet port and permit fluid to enter the fluid cylinder in advance of the resilient washer, a perforate Washer interposed between the uid cylinder and the uid'chamber and adapted to 

